This invention relates to a method for manufacturing .alpha.-sulfo fatty acid ester salt employed as an active component for a detergent composition.
.alpha.-SULFO FATTY ACID ESTER SALT IS PRODUCED BY SULFONATING FATTY ACID ESTER WITH SO.sub.3 and followed by neutralization by alkali. As the sulfonation of fatty acid ester proceeds at a slow speed, it is necessary that the sulfonated product be digested. The coloration of the product is pronounced due to a fair excess of SO.sub.3 and it is therefore necessary that it be subjected to severe bleaching process. Even in this case, it is difficult to obtain a satisfactory color tone. Breakage of ester linkage occurs during the sulfonation, neutralization or bleaching of fatty acid ester. A by-product, for example, .alpha.-sulfo fatty acid di-soda salt yielded by breakage of ester linkage is poor in detergency, when used as an active component for a detergent composition. It is, therefore, desired that the yield or remaining percentage of .alpha.-sulfo fatty acid ester salt be elevated by suppressing the growth of any by-product as much as possible.
A 2-stage sulfonation method, a sulfonated product-esterifying method etc. are proposed for improvement of the fatty acid ester-sulfonating method, but no satisfactory result is obtained owing to the performance of the product as well as the complexity of the process.